Gordon Brown faced embarrassment today when a new poll revealed that voters would rather have former prime ministers Tony Blair and Margaret Thatcher or ex-MP Tony Benn as the country's leader.

The YouGov poll asked voters who they would choose from a list of politicians "at the peak of their powers" to be prime minister. Only 5% chose Brown, while Benn earned 13% and Blair came second with 20%.

Lady Thatcher, the former Tory prime minister, came top of the list with 27%.

The poll, conducted for the Daily Telegraph, found that Brown was unpopular even among Labour voters. Blair was top of the Labour voters' list with 42%, while Brown languished on 10%. Benn scored 17% of the party's voters.

Benn, the leftwing former cabinet minister, was the country's longest-serving Labour MP before retiring from parliament in 2001. He has been a severe critic of New Labour.

In July last year, he made an impassioned plea to the Labour leader to hold a referendum on the EU treaty, something that Brown said would never happen. Benn called the situation "absolutely undemocratic".

Today's poll also revealed that Blair beat Clement Attlee, Labour prime minister from 1945 to 1951, in the contest to decide Britain's greatest post-war prime minister. He came third, while Thatcher was again in first place, with Winston Churchill second.

Brown's popularity has been falling in recent polls, with the past three weeks some of his worst.